In recent years, countermeasures to large-scale disasters of a data center have been required for corporate enterprises. As a countermeasure to large-scale disasters, a remote copy is carried out in which data in a data center is copied to a remote location. For the remote copy, a storage apparatus of a primary data center (hereafter referred to as a primary storage apparatus) receives a write request of data from a host computer, stores the data, and transmits the data to a storage apparatus of a secondary data center of a remote location (hereafter referred to as a secondary storage apparatus).
There are a synchronous type and an asynchronous type for the remote copy. In the case in which data is copied to a secondary storage apparatus of a remote location, an asynchronous remote copy is used generically. For a synchronous remote copy, after a primary storage apparatus that has received a write request from a host computer transmits write data to a secondary storage apparatus, the primary storage apparatus executes a write response to the host computer. Consequently, it takes a long response time to the host computer depending on a distance between the primary storage apparatus and the secondary storage apparatus, therefore deteriorating a response performance.
For an asynchronous remote copy, to a write request from a host computer, the primary storage apparatus stores write data into a data volume (data VOL), stores a journal into a journal volume (JVOL), and transmits a write response to the host computer. After that, the primary storage apparatus transmits a journal to the secondary storage apparatus at a predetermined moment. At this time, in order to maintain the consistency of write data, it is necessary to ensure that a sequence of write data that is written to a data VOL of the secondary storage apparatus based on a journal is equivalent to a sequence of a reception of a write request from the host computer to the primary storage apparatus. Therefore, a sequence number that indicates a sequence of a write request from the host computer is imparted to a journal.
For the asynchronous remote copy, since a load to store a journal is concentrated on the JVOL, a response performance from the host computer to an I/O (Input or Output) is deteriorated unfortunately. Consequently, in an environment containing a plurality of primary storage apparatuses in a primary data center, it is required that a load to treat a journal of the asynchronous remote copy is dispersed to other storage apparatuses in the same data center to be leveled.
In the case in which writing occurs to a plurality of data VOLs in the primary storage apparatus, a journal in which a series of sequence numbers are imparted to the write data that is stored into a plurality of data VOLs is stored into the JVOL. A group for ensuring a write sequence of the write data among a plurality of data VOLs is referred to as a journal group (JNLG). A plurality of data VOLs and the JVOL for storing a journal in which a series of sequence numbers are imparted to the write data that is written to the plurality of data VOLs belong to the JNLG.
As the conventional technology, PTL 1 discloses an asynchronous remote copy system in which all volumes that belong to the JNLG are switched at once and a remote copy is restarted with a subsequent sequence number between a second primary storage apparatus and a secondary storage apparatus during a failure of a first primary storage apparatus by synchronizing sequence numbers of journals in the JNLG of each storage apparatus between a first primary storage apparatus and a second primary storage apparatus for instance.